Japan Geoscience Union Meeting 2016

Presentation information


Symbol M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS17] Paleoclimatology and paleoceanography

Tue. May 24, 2016 9:00 AM - 10:30 AM A04 (APA HOTEL&RESORT TOKYO BAY MAKUHARI)

Convener:*Tomohisa Irino(Faculty of Environmental Earth Science, Hokkaido University), Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University), Akira Oka(Atmosphere and Ocean Research Institute, The University of Tokyo), Yusuke Okazaki(Department of Earth and Planetary Sciences, Graduate School of Science, Kyushu University), Ikuko Kitaba(Research Centre for Palaleoclimatology, Ritsumeikan University), Akihisa Kitamura(Institute of Geosciences, Faculty of Science, Shizuoka University), Masaki Sano(Research Institute for Humanity and Nature), Ryuji Tada(Department of Earth and Planetary Science, Graduate School of Science, The Univeristy of Tokyo), Takeshi Nakagawa(Ritsumeikan University), Akira Hayashida(Department of Environmental Systems Science, Doshisha University), Chair:Akira Hayashida(Department of Environmental Systems Science, Doshisha University)

9:45 AM - 10:00 AM

[MIS17-16] Stalagmite growth and farming by Jomon Man in mid-Holocene

*Akihiro Kano1 (1.Graduate School of Social and Cultural Studies, Kyushu University)

Keywords:stalagmite, Holocene, Jomon

Stalagmite study based on U-Th dating in my laboratory has represented new aspects on the Late Pleistocene-Holocene paleo-moisture in Japanese Islands. In turn, results of the U-Th dating imply that growth of many studied stalagmites slowed or stopped in 4000-6000 years ago although dripwater are still active on these stalagmites. This is clearly due to low Ca concentration of the dripwater, and only a few stalagmites are fed by enough Ca concentration for calcite precipitation. Thus, Ca concentration of dripwaters in Japan decreased in mid-Holocene.
Dripwater Ca concentration is primary controlled by pCO2 at soil/limestone interface where limestone is dissolved. Then, temperature, moisture, and vegetation abundance are main factor for soil CO2 produced by root respiration and microbial decomposition of organic matter. If the soil CO2 in the limestone areas decreased in 4000-6000 years ago, at least one of the factors drastically changed at this period.
Considering relatively stable climate during Holocene, the most likely factor was declined vegetation. In addition, inferring from the age of 4000-6000 years ago, a fundamental cause was farming by Jomon Man that had expanded in Honshu in mid-Holocene. It is well known that they preferred to live in limestone areas because they could hide from rain. Their burnt farming may have destroyed thick forest vegetation and resulted in decreasing soil pCO2 and dripwater Ca, and ultimately in the declined stalagmite growth. We have only little supporting evidence for this hypothesis, but the mid-Holocene peak of fine-grained charcoal in lake deposits implies active farming by Jomon Man. Further examination is required to study detailed charcoal-pollen occurrence in lake deposits, as well to perform radiocarbon dating for burnt wood from the Holocene archeological sites.